Doctor of Medicine, specialist in the Japanese Society of Rehabilitation Medicine, specialist in the Japanese Society of Orthopaedic Surgery, specialist in the Japanese Society of Rheumatology, staff to strengthen JOC, and sports physician certified by the Japan Sports Association
Meniscus injuries occur when jump landings or stop-and-turn balance is disrupted, often with injuries to the medial collateral ligament or the anterior cruciate ligament.
Menisci are located on the medial (inner meniscus: Photo 1) and lateral (outer meniscus) sides of the knee. They help smooth the movement of the knee through an intervening joint surface between the femur and tibia, stabilize the knee joint during knee movement (flexion, extension, and internal and external rotation), and act as a cushion to distribute the impact of jumps and other forces. A meniscus may be damaged (ruptured) when the knee is twisted in sports or other activities. Injuries to a meniscus can cause knee joint pain and limitation of motion.
Photo 1: Injury to the medial meniscus seen with arthroscopy
Most common sports
This injury is more common in sports such as basketball, volleyball, gymnastics, soccer, tennis, baseball, and skiing.
Cause of the injury
It occurs in all situations with knee twisting, but it most often occurs during sports activities. When the knee joint is flexed and rotated (twisted) during jump landing, horizontal stress is applied. The stress may partially or totally damage (rupture) the meniscus. For example, the injury may occur under the following circumstances: when sliding on the floor with one leg, when the knee is hit from the side, or when the knee is flexed valgus and twisted on landing after jumping. It may also sliding on the floor with one foot may occur when the knee is hit from the side of the knee, or when the knee is flexed valgus and twisted during jump landing. It may also result from breaststroke. The main cause of the injury in breaststroke is due to repetitive twisted stress on the knee. Even simple exercises, such as running, may cause the meniscus injuries by wearing the meniscus.
Injury to the anterior cruciate ligament and medial collateral ligament (about 60%) is more likely than injury to the meniscus alone and may be associated with articular cartilage injuries requiring attention. In many cases, the sequelae of isolated anterior cruciate ligament injuries result in loosening of the knee, which can trigger meniscus injury.
Pain is usually the main symptom when a person has just been injured by an acute hit or a single acute stress. The patient constantly has indescribable pain or a feeling of discomfort (catching) like getting lodged when stretching the knee. In the case of large tears in which a part of the meniscus is impacted within the joint, the joint may become unable to extend from a certain angle (locking), causing severe pain and limited range of motion, which may prevent the person from walking (Photo 2). Tenderness at rest and on movement of the knee joint coincide with the location of the meniscus injury. Flexion-extension torsion of the knee joint (McMurray’s test) causes pain. Medial meniscus injuries are five times more common than lateral meniscus injuries.
Photo 2: Unstretchable state due to locking
Chronic arthritis may occur. Effusions or hematomas in the knee joint may develop. Over a more prolonged period, the quadriceps muscle shrinks because the affected side is unconsciously shielded. In more severe cases, the ruptured meniscus collapses, damaging the femoral and tibial cartilages of the knee joint and causing bony deformity (osteoarthritis of the knee).
If the knee joint has any of the above symptoms, the person should first consult an orthopedic specialist to determine the nature and extent of the injury. The meniscus does not appear on the X-ray. Magnetic resonance imaging (MRI) is useful for diagnosis (Photo 3). In the past, arthrography (which looks like a shadow) was the mainstream procedure. However, because MRI is painless and has a very high diagnostic yield of more than 90%, arthrography is now rarely performed. Ultimately, a doctor makes the diagnosis by performing arthroscopy (a procedure in which an endoscope is inserted through a small incision into the knee and viewed with the naked eye through an image showing the inside of the joint, such as the meniscus, ligaments, and articular cartilage).
Photo 3: MRI image of the right knee
The medial meniscus ruptures the bucket handle, and a part of it invaginates inside the knee joint. The cartilage of the inner and outer femur is also injured.
Photo 4 Meniscus: Arthroscopic diagnosis and surgery of damaged joints
Draw the invaginating meniscus while checking the condition with a conductor.
Treatment and rehabilitation
Conservative treatment usually relieves symptoms. Mild cases may be treated with supportive measures, such as braces and taping, and with medications and rehabilitation to relieve pain. Initially, local rest, aspiration of joint fluid by arthrocentesis, local anesthetics, and, more recently, injection of hyaluronic acid (* explanatory note) are mainstream treatments. Previously, steroid injections were given frequently as anti-inflammatory agents, but side effects were noted. Quadriceps muscle exercises and physical therapy (low-frequency or interfering-wave electrical stimulation) around the knee joint are also used to prevent muscle wasting and reduce pain.
Surgery may be done in the presence of rocking symptoms or repeated meniscus injuries, persistent pain, or persistent effusion (water accumulating in the knees) (Photo 4). More recently, the meniscus can be removed endoscopically or sutured for a ruptured margin of the meniscus. (Photo 5) An adequate duration of rehabilitation is essential after surgery. Dynamic rehabilitation is started 2 to 3 weeks after surgery, but strenuous exercise should be avoided until about 2 months after surgery. Complete return to sports is possible in 5-6 months.
Photo 5: The image of endoscopic surgery
* Explanatory note: What is hyaluronic acid
More recently, conservative therapy is effective when sodium hyaluronate (a polysaccharide, such as ARTZ or SUVENYL) is injected into the joint after a meniscus injury. Hyaluronan, also a component of knee articular cartilage, is highly hydrated and substitutes lubricants and cushions in joints when articular cartilage and the meniscus are injured, thereby enhancing movement. It may also help reduce joint pain and swelling. It was originally developed for the treatment of osteoarthritis of the knee in older people, but it has recently been used in athletes. Injections of hyaluronan do not regenerate cartilage. Because the drug is absorbed and lost over time, the effect tends to last longer with several injections, although the duration of the effect is a few days. The research phase also includes the ability of chondrocytes to modulate immune function, and in medical terms, hyaluronan is used to treat periarthritis scapulohumeralis, wrinkles in cosmetic surgery, and in cataract surgery in ophthalmology. It is also sold for use in commercial supplements and other purposes, such as to keep the skin smooth, the evidence for which may be lacking.
Associate Professor, the Department of Regional Medicine, Teikyo Heisei University
A certified athletic trainer from the Japan Sport Association, a practitioner of acupuncture and a massage practitioner
This chapter describes the conditioning of athletes with chronic meniscus injuries.
Quadriceps muscle atrophy is a characteristic feature of chronic cases, as mentioned in the Doctor’s Edition. Muscle strength around the knee joint is also imbalanced, resulting in a decrease in knee joint stability. In addition, the person may unconsciously shift the load to the unaffected side by nursing the affected side , resulting in secondary problems on the unaffected side. Therefore, daily conditioning focuses on increasing muscle strength, particularly in the quadriceps muscle.
On-site evaluation and first aid
Chronic cases include pain in the affected area due to muscle atrophy, knee pain due to muscle weakness, and joint effusion, and they may cause muscle atrophy and lead to a vicious circle. In the athletic field, the degree of muscle atrophy and range of motion of the joints are evaluated to grasp the condition of the functional depression of the knee joint and to deal with the problems.
Joint pain and swelling with warmth may cause new injuries. Icing is performed, and then the person is given weight-bearing relief (using crutches) to help immobilize the knee and seek medical attention.
Points for training in muscle strength for daily conditioning and muscle atrophy in chronic cases
Vastus medialis training
Strengthening vastus medialis is important of the quadriceps muscle. Do this by holding the position for a few seconds in the extension position (Photo A (1)) or by slight external rotation of the extension action (Photo A (2)).
Photo A (1)
Photo A (2)
One method is to use a leg extension machine to (1) advance the vastus medialis slightly further from the extension position while being aware of the external rotation; and to (2) extend the vastus medialis with external rotation so that it is just upward (pay attention not to strengthen external rotation).
Checking the form
Do not break the knee joint position during training, such as in squatting (Photo B). Surgical removal of the meniscus often impairs the stability of the articular surface and tends to increase varus or valgus (a breach). Particular attention should be paid to the "valgus collapse" position, in which the knee enters the medial (middle) side. The form can be effectively adopted when the player checks the mirror.
Photo B (1) Wrong form of valgus collapse – the knee of the stepping leg is inside
Photo B (2) In the correct form, the toes and knees are facing to the front.
Load balance check
Loading on the affected side may result in unconscious shifting of the load to the unaffected side. Such load imbalance can be corrected by riding on a balance disk (board) to perform squatting (Photo C). This training can also be used to improve knee stability.
Picture C Weight-bearing balance check
If there is a load bias, a squat on a balance disk will disrupt the balance during the maneuver.
Combined movement training
Combine hip joint abduction with squatting. Such complex exertion of muscle strength is effective in stabilizing the knee joint and creating the squat form (Photo D). Abduction is done by wrapping the tube around the thigh and keeping the knee straight to resist the load (Photo E).
Photo D Formation
1. If the leg press causes the knee to enter
2. Hold the knee straight to wrap the tube around the thigh to resist the load.
Photo E Squat with hip joint abduction
1. Perform with constant feeling of tube resistance
2. Is more effective when performed on a balance disk
From the unloaded position
Depending on the condition of the affected area, it can be divided into unloaded and weight-bearing positions. If pain or weakness (muscle wasting) is present, the person may begin in a non-weight-bearing position (such as a sitting leg extension machine).